JP2004001264A - Image forming method of reversible thermosensitive recording material - Google Patents

Abstract

In a reversible thermosensitive recording material capable of repeatedly forming and erasing an image by a thermal method, a high-density image can be formed by using a laser, and printing and erasing are repeated many times. Another object of the present invention is to provide an image forming method free from problems such as lowering of color density and occurrence of erasure marks.
In an image forming method for obtaining a reversible thermosensitive recording image by scanning and exposing a laser beam, a dot arrangement pitch in a sub-scanning direction is twice or more a beam coloring radius, and a beam erasing radius and An image forming method for a reversible thermosensitive recording material, characterized in that it is equal to or less than the sum of the coloring radii of the beams.

Description

【００１２】
一般式（１）において、Ｘａ及びＸｂはそれぞれ同じであっても、異なってもよい酸素原子、硫黄原子または両末端に炭化水素原子団を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の基を表す。ここで−ＣＯＮＨ−結合を最小構成単位とする二価の基の具体例としては、アミド（−ＣＯＮＨ−、−ＮＨＣＯ−）、尿素（−ＮＨＣＯＮＨ−）、ウレタン（−ＮＨＣＯＯ−、−ＯＣＯＮＨ−）、ジアシルアミン（−ＣＯＮＨＣＯ−）、ジアシルヒドラジン（−ＣＯＮＨＮＨＣＯ−）、しゅう酸ジアミド（−ＮＨＣＯＣＯＮＨ−）、アシル尿素（−ＣＯＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＯ−）、セミカルバジド（−ＮＨＣＯＮＨＮＨ−、−ＮＨＮＨＣＯＮＨ−）、アシルセミカルバジド（−ＣＯＮＨＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＮＨＣＯ−）、ジアシルアミノメタン（−ＣＯＮＨＣＨ_２ＮＨＣＯ−）、１−アシルアミノ−１−ウレイドメタン（−ＣＯＮＨＣＨ_２ＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＨ_２ＮＨＣＯ−）、マロンアミド（−ＮＨＣＯＣＨ_２ＣＯＮＨ−）等の基が挙げられる。Ｒ^１は単結合または炭素数１から１２の二価の炭化水素基を表す。Ｒ^２は炭素数１から１８の二価の炭化水素基を表す。好ましくは炭素数１から４の二価の炭化水素基である。Ｒ^３は炭素数１から２４の一価の炭化水素基を表し、好ましくは炭素数６から２４の炭化水素基であり、より好ましくは炭素数８から２４の炭化水素基である。更に、Ｒ^１、Ｒ^２及びＲ^３の炭素数の和が１１以上３５以下である場合が特に好ましい。Ｒ^１、Ｒ^２及びＲ^３は主として、各々アルキレン基及びアルキル基を表す。Ｒ^１の場合は、芳香環を含んでいてもよい。ｎは０から４の整数を表し、ｎが２以上のとき繰り返されるＲ^２及びＸｂは同一であっても異なっていてもよい。
【００１３】
本発明に用いられる一般式（１）で示される可逆顕色剤においては、ｎが０で、Ｘａが両末端に炭化水素原子団を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の基であるものが特に好ましい。
【００１４】
以下に一般式（１）で表される具体的化合物を挙げるが、本発明はこれに限定されるものではない。
【００１５】
【化３】

【００１６】
【化４】

【００１７】
本発明に用いられる、一般式（１）で示される可逆顕色剤はそれぞれ１種または２種以上を混合して使用してもよく、通常無色ないし淡色の電子供与性染料前駆体に対する使用量は、５〜５０００重量％、好ましくは１０〜３０００重量％である。
【００１８】
本発明に用いられる、通常無色ないし淡色の電子供与性染料前駆体としては、一般に感圧記録紙や感熱記録紙等に用いられるものがよく知られている。具体的な例としては、例えば下記に挙げるものなどがあるが、本発明はこれに限定されるものではない。またこれら染料前駆体は、それぞれ１種または２種以上を混合して使用してもよい。
【００１９】
（１）トリアリールメタン系化合物
３，３−ビス（ｐ−ジメチルアミノフェニル）−６−ジメチルアミノフタリド（クリスタルバイオレットラクトン）、３，３−ビス（ｐ−ジメチルアミノフェニル）フタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−メチルインドール−３−イル）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−フェニルインドール−３−イル）フタリド、３，３−ビス（１，２−ジメチルインドール−３−イル）−５−ジメチルアミノフタリド、３，３−ビス（１，２−ジメチルインドール−３−イル）−６−ジメチルアミノフタリド、３−（４−ジエチルアミノ−２−ｎ−ヘキシルオキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−アザフタリド、３−（４−ジエチルアミノ−２−メチルフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−アザフタリド、３−（４−ジエチルアミノフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−アザフタリド、３−（４−ジメチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−アザフタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−ｎ−オクチル−２−メチルインドール−３−イル）−４−アザフタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−アザフタリド、３，３−ビス（９−エチルカルバゾール−３−イル）−５−ジメチルアミノフタリド、３，３−ビス（２−フェニルインドール−３−イル）−５−ジメチルアミノフタリド、３−ｐ−ジメチルアミノフェニル−３−（１−メチルピロール−２−イル）−６−ジメチルアミノフタリド等、
【００２０】
（２）ジフェニルメタン系化合物
４，４′−ビス（ジメチルアミノフェニル）ベンズヒドリルベンジルエーテル、Ｎ−クロロフェニルロイコオーラミン、Ｎ−２，４，５−トリクロロフェニルロイコオーラミン等、
【００２１】
（３）キサンテン系化合物
ローダミンＢアニリノラクタム、ローダミンＢ−ｐ−クロロアニリノラクタム、３−ジエチルアミノ−７−ジベンジルアミノフルオラン、３−ジエチルアミノ−７−オクチルアミノフルオラン、３−ジエチルアミノ−７−フェニルフルオラン、３−ジエチルアミノ−７−クロロフルオラン、３−ジエチルアミノ−６−クロロ−７−メチルフルオラン、３−ジエチルアミノ−７−フェノキシフルオラン、３−ジエチルアミノ−７−（３，４−ジクロロアニリノ）フルオラン、３−ジエチルアミノ−７−（２−クロロアニリノ）フルオラン、３−ジエチルアミノ−６−メチル−７−アニリノフルオラン、３−ジエチルアミノ−６−メチル−７−（３−メチルアニリノ）フルオラン、３−（Ｎ−エチル）トリルアミノ−６−メチル−７−アニリノフルオラン、３−ピペリジノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル）トリルアミノ−６−メチル−７−フェネチルフルオラン、３−ジエチルアミノ−７−（４−ニトロアニリノ）フルオラン、３−ジブチルアミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−メチル）プロピルアミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル）イソアミルアミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−メチル）シクロヘキシルアミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル）テトラヒドロフリルアミノ−６−メチル−７−アニリノフルオラン等、
【００２２】
（４）チアジン系化合物
ベンゾイルロイコメチレンブルー、ｐ−ニトロベンゾイルロイコメチレンブルー等、
【００２３】
（５）スピロ系化合物
３−メチルスピロジナフトピラン、３−エチルスピロジナフトピラン、３，３′−ジクロロスピロジナフトピラン、３−ベンジルスピロジナフトピラン、３−メチルナフト−（３−メトキシベンゾ）スピロピラン、３−プロピルスピロベンゾピラン等が挙げられる。
【００２４】
本発明で用いられる可逆性感熱記録層を得るために使用されるバインダーとしては例えば、ポリビニールアルコール、変性ポリビニルアルコール、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、メトキシセルロース、カルボキシメチルセルロース、メチルセルロース、酢酸セルロース、ゼラチン、カゼイン、澱粉、ポリアクリル酸ソーダ、ポリビニルピロリドン、ポリアクリルアミド、アクリル酸アミド／アクリル酸エステル共重合体、アクリル酸アミド／アクリル酸エステル／メタクリル酸３元共重合体、スチレン／無水マレイン酸共重合体のアルカリ塩、エチレン／無水マレイン酸共重合体のアルカリ塩等の水溶性高分子、ポリ酢酸ビニル、ポリアクリル酸エステル、ポリメタクリル酸エステル類、ポリスチレン、スチレン／ブタジエン共重合体、アクリロニトリル／ブタジエン共重合体、アクリル酸メチル／ブタジエン共重合体、エチレン／酢酸ビニル共重合体、エチレン／塩化ビニル共重合体、ポリ塩化ビニル、エチレン／塩化ビニリデン共重合体、ポリ塩化ビニリデン等のラテックス類、フェノキシ樹脂、ポリビニルブチラール樹脂、セルロースアセテートプロピオネート樹脂等およびこれらの水酸基、カルボキシル基がイソシアネート類、アミン類、フェノール類、エポキシ類等の架橋剤と反応し、硬化するポリウレタン等の熱硬化性樹脂、電子線硬化樹脂、紫外線硬化樹脂が挙げられている。これらの中で、特開平１０−２３０６８０号公報や同１１−５８９６３号公報に記載の、ポリオール樹脂をイソシアネート化合物で架橋して得られるポリウレタンが好ましい。
【００２５】
可逆性感熱記録層におけるバインダーの使用量としては、該可逆性感熱記録層全質量に対する該バインダー成分の質量百分率が３５％以上６５％以下の範囲内であることが好ましい。この範囲より大きくなると著しく発色濃度が低下し、逆にこの範囲より小さくなると、可逆性感熱記録層の耐熱性や機械的強度が低下し、層の変形や発色濃度の低下が起きる。可逆性感熱記録層における該バインダー成分の質量百分率は、４０％以上６０％以下がより好ましく、４５％以上５５％以下がなお一層好ましい。
【００２６】
また、可逆性感熱記録層の発色感度および消色温度を調節するための添加剤として、熱可融性物質を可逆性感熱記録層中に含有させることができる。６０℃〜２００℃の融点を有するものが好ましく、特に８０℃〜１８０℃の融点を有するものが好ましい。一般の感熱記録紙に用いられている増感剤を使用することもできる。例えば、Ｎ−ヒドロキシメチルステアリン酸アミド、ステアリン酸アミド、パルミチン酸アミドなどのワックス類、２−ベンジルオキシナフタレン等のナフトール誘導体、ｐ−ベンジルビフェニル、４−アリルオキシビフェニル等のビフェニル誘導体、１，２−ビス（３−メチルフェノキシ）エタン、２，２′−ビス（４−メトキシフェノキシ）ジエチルエーテル、ビス（４−メトキシフェニル）エーテル等のポリエーテル化合物、炭酸ジフェニル、シュウ酸ジベンジル、シュウ酸ビス（ｐ−メチルベンジル）エステル等の炭酸またはシュウ酸ジエステル誘導体等を併用して添加することができる。
【００２７】
本発明の可逆性感熱記録層の膜厚は０．１〜２０μｍの範囲が好ましく、３〜１５μｍがより好ましい。
【００２８】
本発明においては、可逆性感熱記録材料、特に通常無色ないし淡色の染料前駆体と、加熱によりこの染料前駆体を発色させ、これを再加熱して消色させる可逆顕色剤の組み合わせからなる可逆性感熱記録層を含む可逆性感熱記録材料に対して、一定の条件下にレーザー光を走査露光することで高濃度の画像形成を可能にしている。ここで、この可逆性感熱記録層中に、近赤外部に吸収を有する光熱変換材料を含有させるか、あるいは、該光熱変換材料を含有する光熱変換層を可逆性感熱記録層に直接隣接して設けることにより、より低いレーザー光エネルギーでの印字が可能となるため、印字消去を多数回繰り返しても、発色濃度の低下や消去跡の発生といった問題がなくなり、より好ましい。
【００２９】
本発明に用いられる、近赤外部に吸収を有する光熱変換材料としては、たとえば白金、チタン、シリコン、クロム、ニッケル、ゲルマニウム、アルミニウムなどの金属または半金属の層、日本化薬製のＩＲＧ００２（商品名）やＩＲＧ０２２（商品名）等のインモニウム化合物、金属錯体化合物、シアニン色素、スクワリリウム色素、ナフトキノン色素、フタロシアニン化合物等が挙げられるがこれらに限定されるものではない。好ましい光熱変換材料としては、光熱変換効率、溶剤への溶解性、樹脂への分散性の点でフタロシアニン化合物及び金属錯体化合物が挙げられる。
【００３０】
フタロシアニン化合物の例としては、ナフタロシアニン化合物、無金属フタロシアニン化合物、鉄フタロシアニン化合物、銅フタロシアニン化合物、亜鉛フタロシアニン化合物、ニッケルフタロシアニン化合物、バナジルフタロシアニン化合物、塩化インジウムフタロシアニン化合物、塩化錫フタロシアニン化合物等が好ましく、より好ましくは銅フタロシアニン化合物、バナジルフタロシアニン化合物、亜鉛フタロシアニン化合物である。本発明に用いられるフタロシアニン化合物は吸収波長の調節、溶媒への溶解度の向上、耐光性の改良等の目的で、芳香環に置換基を有しても良い。置換基としては、アルキルエーテル基、アルキルチオエーテル基、アリールエーテル基、アリールチオエーテル基、アミド基、アミノ基、アルキルエステル基、アリールエステル基、塩素原子、フッ素原子等が挙げられる。芳香環に置換基が二つ以上ある場合に、置換基同士が環を形成しても良い。また金属錯体化合物としては、ニッケルジチオール錯体やインドアニリン金属錯体等が挙げられる。
【００３１】
光熱変換材料は単独使用はもとより、２種類以上を混合して用いることができる。その添加量は１ｍｇ／ｍ^２から２００ｍｇ／ｍ^２が適当であり、５ｍｇ／ｍ^２から５０ｍｇ／ｍ^２が好ましい。この量より少ないと画像消去に必要なエネルギーを十分に低減できず、印字消去の繰り返し特性が劣化する。またこの量より多いと、光熱変換材料が若干なりとも有している可視部の吸収が大きくなりすぎて画像の視認性が低下する。
【００３２】
印字に使用するレーザーとしては炭酸ガスレーザー、半導体レーザー、ＹＡＧレーザー等を挙げることができるが、装置を小型化できるという点で、半導体レーザー、ＹＡＧレーザーが好ましい。
【００３３】
画像を消去する方法としては、サーマルヘッドを用いて加熱消去する方法、熱ロールあるいは熱板を用いて加熱消去する方法、熱光源を用いて加熱消去する方法等があるが、本発明における消去方法としては特に制限はない。
【００３４】
本発明の可逆性感熱記録材料に用いられる支持体としては、紙、各種不織布、織布、合成樹脂フィルム、合成樹脂ラミネート紙、合成紙、金属箔、ガラス等、あるいはこれらを組み合わせた複合シートを目的に応じて任意に用いることができるし、さらに、透明、半透明或いは不透明のいずれであっても良い。また、これらに限定されるものでもない。
【００３５】
本発明の可逆性感熱記録材料を構成する各層を支持体上に形成する方法は特に制限されるものではなく、従来の方法により形成することができる。例えば、エアーナイフコーター、ブレードコーター、バーコーター、カーテンコーター等の塗抹装置、平板、凸版、凹版、フレキソ、グラビア、スクリーン、ホットメルト等の方式による各種印刷機等を用いることができる。さらに通常の乾燥工程の他、ＵＶ照射・ＥＢ照射により各層を保持させることができる。これらの方法により、１層ずつあるいは多層同時に塗抹、印刷することができる。
【００３６】
本発明の可逆性感熱記録材料は、加熱により画像の書き込みと消去を繰り返し行うものであるが、サーマルヘッド、熱ロール、熱バー、熱スタンプ、ガイドレール等の接触部材による機械的損傷を防止するため、保護層を設けてもよく、また、日常の環境下での光曝露による染料前駆体の劣化を防止するために紫外線吸収剤や酸化防止剤を含有する層や酸素バリア層を設けてもよく、設ける順序は可逆性感熱記録層上であればどちらが上でも構わない。この場合、これらの層は２層ないしは３層以上の複数の層から構成されていてもよい。また、基材との接着性や各層間での層間接着強度を上げるための接着層や、断熱層をそれぞれ設けてもよい。さらに、可逆性感熱記録層が設けられている面または反対側の面に、電気的、磁気的、光学的に情報が記録可能な材料を含んでもよい。また、可逆性感熱記録層が設けられている面と反対側の面に、カール防止、帯電防止を目的としてバックコート層を設けてもよく、さらに粘着加工等を行ってもよい。
【００３７】
また、可逆性感熱記録層や保護層等には、ケイソウ土、タルク、カオリン、焼成カオリン、炭酸カルシウム、炭酸マグネシウム、酸化チタン、酸化亜鉛、酸化ケイ素、水酸化アルミニウム、尿素−ホルマリン樹脂等の顔料、その他に、ステアリン酸亜鉛、ステアリン酸カルシウム等の高級脂肪酸金属塩、パラフィン、酸化パラフィン、ポリエチレン、酸化ポリエチレン、ステアリン酸アミド、カスターワックス等のワックス類を、また、ジオクチルスルホコハク酸ナトリウム等の分散剤、さらに界面活性剤、蛍光染料などを含有させることもできる。
【００３８】
【実施例】
以下実施例によって本発明を更に詳しく説明する。なお実施例中の部数や百分率は質量基準である。
【００３９】
実施例１
［可逆性感熱記録材料（１）の作製］
３−ジエチルアミノ−６−メチル−７−ｍ−トリフルオロメチルフェニルアミノフルオラン（山田化学（株）製、ＢＬＡＣＫ　１００）２０部、Ｎ−［３−（ｐ−ヒドロキシフェニル）プロピオノ］−Ｎ′−ｎ−ドコサノヒドラジド１００部、光熱変換材料（山本化学（株）製、ＹＫＲ−３０７０）１部、ポリエステルポリオール（大日本インキ化学工業（株）製、バーノックＤ−２９３−７０）５０部、硬化剤（日本ポリウレタン（株）製、コロネートＨＬ）５０部、メチルエチルケトン３００部、トルエン３００部の混合物を、ガラスビーズと共にペイントシェーカーで５時間粉砕した。得られた分散液をポリエチレンテレフタレート（ＰＥＴ）シートにそれぞれ固形分５ｇ／ｍ^２となる様に塗工した。得られた可逆性感熱記録層の上に、ウレタンアクリレート系紫外線硬化樹脂（大日本インキ製Ｃ７−１５７）１５部、メチルエチルケトン８５部とをよく混合した上で塗工し、１２０℃で１分間乾燥した後、照射エネルギー８０Ｗ／ｃｍの紫外線ランプ下を９ｍ／分の搬送速度で通して硬化させ、膜厚３μｍの保護層を設けて、可逆性感熱記録材料（１）を作製した。
【００４０】
試験１（条件１におけるビームの発色半径と消色半径の測定）
実施例１で作製した可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて印加パルス１．０ミリ秒で印加電圧２６ボルトの条件で印字した。得られた発色部と非発色部に、出力６５０ｍＷ、波長８３０ｎｍの半導体レーザーからのレーザー光を集光し、照射エネルギー１．５Ｊ／ｃｍ^２として印字した画像より、発色半径７５μｍ、消色半径が１３５μｍであることがわかった。
【００４１】
試験２（条件２におけるビームの発色半径と消色半径の測定）
照射エネルギーを１．８Ｊ／ｃｍ^２とする以外は試験１と同様に操作したところ、この条件における発色半径が８５μｍ、消色半径が１８５μｍであることがわかった。
【００４２】
試験３（ドット配列ピッチを変えた印字実験）
実施例１で作製した可逆性感熱記録材料に対して、表１に示すように副走査方向のドット配列ピッチを変えて走査露光印字した。発色画像部の濃度を濃度計マクベスＲＤ９１８を用いて測定して、ドット配列ピッチに対してプロットしたところ、条件１では、配列ピッチが「ビームの発色半径の２倍」＝１５０μｍ以上、「ビームの消色半径とビームの発色半径の和」＝２１０μｍ以下の範囲にある１５０μｍと２００μｍで高い画像濃度が得られた。条件２においても同様に、配列ピッチが「ビームの発色半径の２倍」＝１７０μｍ以上、「ビームの消色半径とビームの発色半径の和」＝２７０μｍ以下の範囲にある２００μｍと２５０μｍで高い画像濃度が得られた。またこれらの印字サンプルを５００Ｗのハロゲンランプから３ｃｍ離して設置し、５秒間照射すると、ほぼ地肌濃度まで消去され、消去跡もほとんど認められなかった。同様の操作を５００回繰り返したが、発色濃度の低下や消去跡の発生は見られなかった。
【００４３】
【表１】

【００４４】
【発明の効果】
本発明によれば、レーザー光を走査露光することにより可逆性感熱記録画像を得る画像形成方法において、副走査方向のドット配列ピッチが、ビームの発色半径の２倍以上であり、ビームの消色半径とビームの発色半径の和以下とすることにより、高濃度の画像形成が可能であり、印字消去を多数回繰り返しても、発色濃度の低下や消去跡の発生がない。
【図面の簡単な説明】
【図１】本発明の原理説明図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a recording method for a reversible thermosensitive recording material whose color tone changes reversibly by controlling thermal energy.
[0002]
[Prior art]
In recent years, reversible thermosensitive recording materials that can form a temporary image and allow the image to be erased when it is no longer needed have attracted attention. A typical example thereof is a colorless or pale-colored dye precursor, and a reversible thermosensitive recording material using a reversible developer that causes the dye precursor to develop color by heating, and then reheats and decolorizes it. Are known. Examples of such reversible thermosensitive recording materials include those described in JP-A-6-210954, JP-A-6-171225, JP-A-7-68934, JP-A-7-179043, and the like. it can.
[0003]
Generally, as a method of forming an image of such a reversible thermosensitive recording material, a method using a thermal head and a method using thermal energy of a laser beam are known. As a method of erasing an image, a method of erasing by heating using a thermal head, a method of erasing by heating using a hot roll or a hot plate, a method of using a heat light source, and the like are used. The method of forming an image using a thermal head has the advantage of making the apparatus compact, but has the problem that the heat is easily applied to the reversible thermosensitive recording material due to the high heat and pressure from the thermal head. is there. Although a countermeasure is provided by providing a protective layer and the like, the durability has been achieved only at most several hundred times. On the other hand, the method using the thermal energy of a laser beam is advantageous in that durability is improved because a mechanical shock is not directly applied to the reversible thermosensitive recording material. Also, there is an advantage that the degree of freedom of the shape of the recording medium to which the reversible thermosensitive recording material is attached is greater than when a thermal head is used. However, according to the study of the present inventors, it has been clarified that when recording is performed on a reversible thermosensitive material using thermal energy of a laser beam, there is a problem due to reversibility. That is, when laser irradiation is performed in the vicinity of an already printed portion, a new print is generated, and at the same time, the already printed portion is erased concentrically with the printed portion. When forming an image while scanning and exposing a laser beam, if the dot arrangement pitch in the sub-scanning direction is too short, in extreme cases, each print will be erased in the next printing stage, This means that almost no image can be obtained.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide an image forming method capable of forming a high-density image using a laser in a reversible thermosensitive recording material capable of repeatedly forming and erasing an image by a thermal method. . Another object of the present invention is to provide a method for forming an image on a reversible thermosensitive recording material which does not cause a problem such as a decrease in color density or generation of an erase mark even when printing and erasing are repeated many times.
[0005]
[Means for Solving the Problems]
The present inventors have conducted intensive research and have found that, in an image forming method for obtaining a reversible thermosensitive recording image by scanning and exposing a laser beam, the dot arrangement pitch in the sub-scanning direction is at least twice the coloring radius of the beam. It has been found that the above-mentioned problems can be solved by an image forming method for a reversible thermosensitive recording material, wherein the image forming method is not more than the sum of the decoloring radius of the beam and the coloring radius of the beam. .
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
As the reversible thermosensitive recording material used in the present invention, those in which a transparent state and a cloudy state are reversibly changed by a thermal method, and those in which a colored state and a decolored state are reversibly changed are known. . As the specific form of the former, there is one in which an organic low-molecular substance is dispersed in a polymer base material, and in the latter, a colorless or pale-color dye precursor is usually used, and the dye precursor is colored by heating, There is a combination of a reversible color developer that reheats and decolors it. In the present invention, the latter combination of the dye precursor / reversible color developer is preferred because of excellent image visibility.
[0007]
In the present invention, in an image forming method for obtaining a reversible thermosensitive recording image by scanning and exposing a laser beam, the dot arrangement pitch in the sub-scanning direction is set to be at least twice the beam coloring radius, the beam decoloring radius and the beam Are characterized by being equal to or less than the sum of the coloring radii. This will be described in more detail with reference to FIG.
[0008]
In FIG. 1, the horizontal direction is the main scanning direction, and the vertical direction is the sub-scanning direction. After printing the upper spot, the laser beam turned back, and the lower spot was printed. In the figure, A indicates the dot arrangement pitch (pitch interval in the sub-scanning direction), B indicates the beam coloring radius, and C indicates the beam erasing radius. In case 1, A> B + C, and the upper spot is not erased, but a small printable margin remains. In Case 4, A <2B, and the wide portion of the upper spot printed earlier is erased by later printing. According to the study of the present inventors, in order to obtain a high color density, the dot arrangement pitch should be not less than twice the beam coloring radius and not more than the sum of the beam decoloring radius and the beam coloring radius. Was needed.
[0009]
The decoloring radius of the beam is affected by various factors such as the energy intensity of the beam, the heat capacity and the thermal conductivity of the reversible thermosensitive recording material. Actually, it can be obtained experimentally by forming a solid printing portion in advance with a heat stamp or the like and performing laser printing on this portion. The color developing radius of the beam can be determined from the color obtained by irradiating the laser beam to the non-printed portion.
[0010]
As the reversible developer that causes the dye precursor to undergo a reversible color change upon heating, a known reversible developer used in the present invention can be used. Above all, those represented by the following general formula (1) are preferable, but the present invention is not limited thereto.
[0011]
Embedded image

[0012]
In the general formula (1), Xa and Xb may be the same or different, and may be the same as or different from each other. Divalent having a minimum constituent unit of an oxygen atom, a sulfur atom, or a -CONH-bond containing no hydrocarbon atom group at both terminals. Represents a group. Here, specific examples of the divalent group having a —CONH— bond as a minimum constituent unit include amide (—CONH—, —NHCO—), urea (—NHCONH—), urethane (—NHCOO—, —OCONH—). , Diacylamine (-CONHCO-), diacylhydrazine (-CONHNHCO-), oxalic acid diamide (-NHCONCONH-), acylurea (-CONHCONH-, -NHCONHCO-), semicarbazide (-NHCONHNH-, -NHNHCONH-), acyl Semicarbazide (-CONHNHCONH-, -NHCONHNHCO-), diacylaminomethane (-CONHCH ₂ NHCO-), 1-acylamino-1-ureidomethane (-CONHCH ₂ NHCONH-, -NHCONHCH ₂ NHCO-), malonamide (-NHCOCH) ₂ CONH-) and the like. R ¹ Represents a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms. R ² Represents a divalent hydrocarbon group having 1 to 18 carbon atoms. It is preferably a divalent hydrocarbon group having 1 to 4 carbon atoms. R ³ Represents a monovalent hydrocarbon group having 1 to 24 carbon atoms, preferably a hydrocarbon group having 6 to 24 carbon atoms, and more preferably a hydrocarbon group having 8 to 24 carbon atoms. Further, R ¹ , R ² And R ³ It is particularly preferred that the sum of the carbon numbers of the compounds is from 11 to 35. R ¹ , R ² And R ³ Represents mainly an alkylene group and an alkyl group, respectively. R ¹ In the case of, an aromatic ring may be contained. n represents an integer of 0 to 4, and R is repeated when n is 2 or more. ² And Xb may be the same or different.
[0013]
In the reversible developer represented by the general formula (1) used in the present invention, n is 0, and Xa is a divalent dye having a -CONH-bond having no hydrocarbon atom group at both terminals as a minimum constitutional unit. Those which are groups are particularly preferred.
[0014]
Specific compounds represented by the general formula (1) are shown below, but the present invention is not limited thereto.
[0015]
Embedded image

[0016]
Embedded image

[0017]
The reversible developer represented by the general formula (1) used in the present invention may be used alone or as a mixture of two or more thereof, and is usually used in a colorless or pale color electron-donating dye precursor. Is 5 to 5000% by weight, preferably 10 to 3000% by weight.
[0018]
As the usually colorless or light-colored electron-donating dye precursor used in the present invention, those generally used for pressure-sensitive recording paper, heat-sensitive recording paper, and the like are well known. Specific examples include, for example, the following, but the present invention is not limited thereto. These dye precursors may be used alone or in combination of two or more.
[0019]
(1) Triarylmethane compounds
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) ) -3- (1-Ethyl-2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethyl) Aminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1 , 2-Dimethylindol-3-yl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-n-hexyloxyphenyl) -3- 1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-methylphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4- Azaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-dimethylamino-2-ethoxyphenyl) -3- (1 -Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-n-octyl-2-methylindol-3-yl) -4 -Azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3,3-bi (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3 -(1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like,
[0020]
(2) Diphenylmethane compounds
4,4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, etc.
[0021]
(3) Xanthene compounds
Rhodamine B anilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-phenylfluoran, 3 -Diethylamino-7-chlorofluoran, 3-diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-7-phenoxyfluoran, 3-diethylamino-7- (3,4-dichloroanilino) fluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (3-methylanilino) fluoran, 3- (N- Ethyl) tolylamino-6-methyl-7-anilinov Oran, 3-piperidino-6-methyl-7-anilinofluoran, 3- (N-ethyl) tolylamino-6-methyl-7-phenethylfluoran, 3-diethylamino-7- (4-nitroanilino) fluoran, 3 -Dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl) propylamino-6-methyl-7-anilinofluoran, 3- (N-ethyl) isoamylamino-6-methyl- 7-anilinofluoran, 3- (N-methyl) cyclohexylamino-6-methyl-7-anilinofluoran, 3- (N-ethyl) tetrahydrofurylamino-6-methyl-7-anilinofluoran and the like ,
[0022]
(4) Thiazine compounds
Benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.
[0023]
(5) Spiro compounds
3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 3-propyl Spirobenzopyran and the like.
[0024]
As the binder used to obtain the reversible thermosensitive recording layer used in the present invention, for example, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, methoxycellulose, carboxymethylcellulose, methylcellulose, cellulose acetate, gelatin, Casein, starch, sodium polyacrylate, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer Water-soluble polymers such as alkali salts of ethylene, alkali salts of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyacrylates, polymethacrylates, polystyrene, polystyrene / Butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl chloride copolymer, polyvinyl chloride, ethylene / vinylidene chloride copolymer Latexes such as polyvinylidene chloride, phenoxy resin, polyvinyl butyral resin, cellulose acetate propionate resin and the like, and their hydroxyl groups and carboxyl groups react with a crosslinking agent such as isocyanates, amines, phenols and epoxies, A thermosetting resin such as a polyurethane that cures, an electron beam curing resin, and an ultraviolet curing resin are mentioned. Among these, polyurethanes obtained by crosslinking a polyol resin with an isocyanate compound described in JP-A-10-230680 and JP-A-11-58963 are preferable.
[0025]
The amount of the binder used in the reversible thermosensitive recording layer is preferably such that the mass percentage of the binder component with respect to the total mass of the reversible thermosensitive recording layer is in the range of 35% to 65%. If it is larger than this range, the color density is significantly reduced, and if it is smaller than this range, the heat resistance and mechanical strength of the reversible thermosensitive recording layer are reduced, and the layer is deformed and the color density is reduced. The mass percentage of the binder component in the reversible thermosensitive recording layer is more preferably from 40% to 60%, and even more preferably from 45% to 55%.
[0026]
In addition, a thermofusible substance can be contained in the reversible thermosensitive recording layer as an additive for adjusting the color development sensitivity and the decoloring temperature of the reversible thermosensitive recording layer. Those having a melting point of 60 ° C to 200 ° C are preferred, and those having a melting point of 80 ° C to 180 ° C are particularly preferred. A sensitizer used in general thermosensitive recording paper can also be used. For example, waxes such as N-hydroxymethylstearic acid amide, stearic acid amide, and palmitic acid amide; naphthol derivatives such as 2-benzyloxynaphthalene; biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl; Polyether compounds such as -bis (3-methylphenoxy) ethane, 2,2'-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl) ether, diphenyl carbonate, dibenzyl oxalate, bis (oxalate) Carbonic acid or oxalic acid diester derivatives such as (p-methylbenzyl) ester can be added in combination.
[0027]
The thickness of the reversible thermosensitive recording layer of the invention is preferably in the range of 0.1 to 20 μm, more preferably 3 to 15 μm.
[0028]
In the present invention, a reversible thermosensitive recording material, particularly a colorless or pale-color dye precursor, and a reversible developer comprising a combination of a reversible color developer that forms a color of the dye precursor by heating and decolorizes by reheating the dye precursor. A high-density image can be formed by scanning and exposing a reversible thermosensitive recording material including a thermosensitive recording layer with a laser beam under certain conditions. Here, in this reversible thermosensitive recording layer, a light-to-heat conversion material having absorption in the near infrared region is contained, or the light-to-heat conversion layer containing the light-to-heat conversion material is directly adjacent to the reversible thermosensitive recording layer. By providing such a layer, it is possible to perform printing with lower laser light energy. Therefore, even if printing and erasing are repeated many times, problems such as a decrease in color density and generation of erasure traces are eliminated, which is more preferable.
[0029]
Examples of the photothermal conversion material having absorption in the near infrared region used in the present invention include metal or semimetal layers such as platinum, titanium, silicon, chromium, nickel, germanium, and aluminum, and IRG002 manufactured by Nippon Kayaku (commercially available). Compounds, metal complex compounds, cyanine dyes, squarylium dyes, naphthoquinone dyes, phthalocyanine compounds, and the like, but are not limited thereto. Preferred light-to-heat conversion materials include phthalocyanine compounds and metal complex compounds in terms of light-to-heat conversion efficiency, solubility in a solvent, and dispersibility in a resin.
[0030]
As examples of the phthalocyanine compound, naphthalocyanine compounds, metal-free phthalocyanine compounds, iron phthalocyanine compounds, copper phthalocyanine compounds, zinc phthalocyanine compounds, nickel phthalocyanine compounds, vanadyl phthalocyanine compounds, indium chloride phthalocyanine compounds, tin chloride phthalocyanine compounds and the like are more preferable. Preferred are copper phthalocyanine compounds, vanadyl phthalocyanine compounds, and zinc phthalocyanine compounds. The phthalocyanine compound used in the present invention may have a substituent on the aromatic ring for the purpose of adjusting absorption wavelength, improving solubility in a solvent, improving light resistance, and the like. Examples of the substituent include an alkyl ether group, an alkyl thio ether group, an aryl ether group, an aryl thio ether group, an amide group, an amino group, an alkyl ester group, an aryl ester group, a chlorine atom, and a fluorine atom. When the aromatic ring has two or more substituents, the substituents may form a ring. Examples of the metal complex compound include a nickel dithiol complex and an indoaniline metal complex.
[0031]
The photothermal conversion material can be used alone or in combination of two or more. The addition amount is 1 mg / m ² To 200mg / m ² Is suitable and 5 mg / m ² To 50mg / m ² Is preferred. If the amount is less than this, the energy required for image erasure cannot be sufficiently reduced, and the repetition characteristics of print erasure will deteriorate. On the other hand, if the amount is larger than this, the absorption of the visible portion of the photothermal conversion material at least slightly becomes too large, and the visibility of the image is reduced.
[0032]
Examples of the laser used for printing include a carbon dioxide gas laser, a semiconductor laser, and a YAG laser. However, a semiconductor laser and a YAG laser are preferable in that the apparatus can be downsized.
[0033]
Examples of the method of erasing an image include a method of erasing by heating using a thermal head, a method of erasing by heating using a hot roll or a hot plate, a method of erasing by heating using a heat light source, and the like. There is no particular limitation.
[0034]
Examples of the support used in the reversible thermosensitive recording material of the present invention include paper, various nonwoven fabrics, woven fabrics, synthetic resin films, synthetic resin laminated paper, synthetic paper, metal foil, glass, and the like, or a composite sheet combining these. It can be used arbitrarily according to the purpose, and may be transparent, translucent or opaque. Further, the present invention is not limited to these.
[0035]
The method for forming each layer constituting the reversible thermosensitive recording material of the present invention on a support is not particularly limited, and it can be formed by a conventional method. For example, a smearing apparatus such as an air knife coater, a blade coater, a bar coater, and a curtain coater, and various printing machines using a flat plate, letterpress, intaglio, flexo, gravure, screen, hot melt, or the like can be used. Further, each layer can be held by UV irradiation and EB irradiation in addition to the usual drying step. By these methods, smearing and printing can be performed one layer at a time or simultaneously at multiple layers.
[0036]
The reversible thermosensitive recording material of the present invention repeatedly writes and erases an image by heating, but prevents mechanical damage due to contact members such as a thermal head, a heat roll, a heat bar, a heat stamp, and a guide rail. Therefore, a protective layer may be provided, or a layer containing an ultraviolet absorber or an antioxidant or an oxygen barrier layer may be provided to prevent deterioration of the dye precursor due to light exposure in a daily environment. The order in which the layers are provided may be on the reversible thermosensitive recording layer. In this case, these layers may be composed of two or three or more layers. Further, an adhesive layer for increasing the adhesiveness to the base material or the interlayer adhesive strength between the layers, or a heat insulating layer may be provided. Further, the surface on which the reversible thermosensitive recording layer is provided or the surface on the opposite side may include a material capable of recording information electrically, magnetically, and optically. Further, a back coat layer may be provided on the surface opposite to the surface on which the reversible thermosensitive recording layer is provided for the purpose of preventing curling and electrification, and may be further subjected to adhesive processing or the like.
[0037]
In addition, pigments such as diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, and urea-formalin resin are used for the reversible thermosensitive recording layer and the protective layer. , In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearic acid amide, caster wax, and dispersants such as sodium dioctyl sulfosuccinate; Further, a surfactant, a fluorescent dye and the like can be contained.
[0038]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples. In the examples, parts and percentages are based on mass.
[0039]
Example 1
[Preparation of reversible thermosensitive recording material (1)]
20 parts of 3-diethylamino-6-methyl-7-m-trifluoromethylphenylaminofluoran (BLACK 100, manufactured by Yamada Chemical Co., Ltd.), N- [3- (p-hydroxyphenyl) propiono] -N'- 100 parts of n-docosanohydrazide, 1 part of photothermal conversion material (YKR-3070, manufactured by Yamamoto Chemical Co., Ltd.), 50 parts of polyester polyol (Bernock D-293-70, manufactured by Dainippon Ink and Chemicals, Inc.), curing A mixture of 50 parts of an agent (Coronate HL, manufactured by Nippon Polyurethane Co., Ltd.), 300 parts of methyl ethyl ketone, and 300 parts of toluene was ground together with glass beads by a paint shaker for 5 hours. A solid content of 5 g / m was applied to a polyethylene terephthalate (PET) sheet. ² It was applied so that On the obtained reversible thermosensitive recording layer, 15 parts of a urethane acrylate-based UV-curable resin (C7-157 made by Dainippon Ink) and 85 parts of methyl ethyl ketone were mixed well, coated, and dried at 120 ° C. for 1 minute. After that, the composition was cured by passing it under an ultraviolet lamp having an irradiation energy of 80 W / cm at a transport speed of 9 m / min, and a protective layer having a thickness of 3 μm was provided to produce a reversible thermosensitive recording material (1).
[0040]
Test 1 (Measurement of beam coloring radius and erasing radius under condition 1)
The reversible thermosensitive recording material prepared in Example 1 was applied with an applied voltage of 26 volts with an applied pulse of 1.0 millisecond using an Okura Electric thermal facsimile printing tester TH-PMD with a Kyocera print head KJT-256-8MGF1. Printed under conditions. A laser beam from a semiconductor laser having an output of 650 mW and a wavelength of 830 nm was condensed on the obtained color-forming portion and the non-color-forming portion, and irradiation energy was 1.5 J / cm. ² From the image printed as, it was found that the coloring radius was 75 μm and the erasing radius was 135 μm.
[0041]
Test 2 (Measurement of beam coloring radius and erasing radius under condition 2)
Irradiation energy 1.8 J / cm ² The same operation as in Test 1 was carried out, except that the coloring radius was 85 μm and the erasing radius was 185 μm under these conditions.
[0042]
Test 3 (Printing experiment with different dot arrangement pitch)
The reversible thermosensitive recording material prepared in Example 1 was subjected to scanning exposure printing by changing the dot arrangement pitch in the sub-scanning direction as shown in Table 1. When the density of the color image portion was measured using a densitometer Macbeth RD918 and plotted against the dot array pitch, under the condition 1, the array pitch was “twice the beam coloring radius” = 150 μm or more, and High image densities were obtained at 150 μm and 200 μm in the range of “sum of the decoloring radius and the coloring radius of the beam” = 210 μm or less. Similarly in the condition 2, images having high arrangement pitches of 200 μm and 250 μm in the range of “double the beam coloring radius” = 170 μm or more and “sum of beam decoloring radius and beam coloring radius” = 270 μm or less The concentration was obtained. When these printed samples were placed at a distance of 3 cm from a 500 W halogen lamp and irradiated for 5 seconds, they were almost erased to the background density, and almost no erased marks were observed. The same operation was repeated 500 times, but no decrease in the color density or generation of an erasure trace was observed.
[0043]
[Table 1]

[0044]
【The invention's effect】
According to the present invention, in the image forming method for obtaining a reversible thermosensitive recording image by scanning and exposing a laser beam, the dot arrangement pitch in the sub-scanning direction is twice or more the beam coloring radius, and the beam is erased. By making the radius equal to or less than the sum of the radius of the beam and the coloring radius of the beam, a high density image can be formed.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the principle of the present invention.

Claims (5)

In an image forming method for obtaining a reversible thermosensitive recording image by scanning and exposing a laser beam, the dot arrangement pitch in the sub-scanning direction is twice or more the beam coloring radius, the beam decoloring radius and the beam coloring radius. The method for forming an image of a reversible thermosensitive recording material, characterized by being not more than the sum of A reversible thermosensitive recording material is a colorless or pale-colored dye precursor, and a reversible thermosensitive recording layer composed of a combination of a reversible developer that causes the dye precursor to develop a color by heating, and reheats and decolorizes the recurable developer. The image forming method according to claim 1, further comprising: In the reversible thermosensitive recording layer, a light-to-heat conversion material having absorption in the near infrared region is contained, or the light-to-heat conversion layer containing the light-to-heat conversion material is provided directly adjacent to the reversible thermosensitive recording layer. The image forming method according to claim 1, wherein: The image forming method according to claim 1, wherein the laser is a semiconductor laser or a YAG laser. The image forming method according to claim 2, wherein the reversible developer is a compound represented by the following general formula (1).

(In the compound represented by the general formula (1), Xa and Xb may be the same or different, and the oxygen atom, sulfur atom, or -CONH-bond containing no hydrocarbon atom group at both terminals is minimized. R ¹ represents a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms, R ² represents a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ³ represents a carbon atom. Represents a monovalent hydrocarbon group represented by Formulas 1 to 24. n represents an integer of 0 to 4, and when n is 2 or more, R ² and Xb repeated may be the same or different.)

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